The goal of this project is to provide support of National Toxicology Program (NTP) hazard identification activities targeted toward the prevention of diseases or adverse effects caused by environmental exposure to nanomaterials. Toxicity testing is an important aspect of public health research in that it serves to identify chemicals that are hazardous to human health. Proper chemical analyses are required to ensure that, in toxicity studies, the test species are exposed to the prescribed chemicals at the specified dose concentrations. This contract contributes to the ability of toxicity studies to provide evidence of heightened cancer risk along with other toxicological outcomes, by providing characterization of the chemicals studied, confirmation of the dose levels administered, and internal dose determinations. This information is critical to evaluation of toxicity tests and development of sound, scientific conclusions about the potential toxicity of the study chemical in the test species and ultimately supports the risk assessment efforts of National Toxicology Program and other federal agencies. With internal dose information provided by this contract, extrapolations to humans can be made so that the public can be adequately informed about risk factors arising from exposure to studied chemicals. During FY10, 39 tasks were begun, performed, and/or completed in support of NTP and DIR Nanomaterials research and testing protocols. Additional characterization was performed for 5 of the 24, multiwalled carbon nanotubes (MWCNT) procured last year from different vendors. MWCNTs were characterized as to zeta potential, Brunauer, Emmett, Teller (BET) surface area, and Scanning Electron Microscopy (SEM) measurements of the dimensions of the undispersed material. In support of the NIEHS Clinical Research program, nanoscale ceric oxide formulations were analyzed to determine (i) absorption of ceric oxide nanoparticles at 633 nm, (ii) refractive index of ceric oxide nanoparticles (bulk, dry material) and the two dispersants, (iii) viscosity of the two dispersants at 25 deg, and (iv) dielectric constant of the two dispersants